Press for plywood



Oct. 5, 1937. A. R. WELCH PRESS FOR PLYWOOD 4 Filed Nov. 26, 1934 3Sheets-Sheet 1 Armz r R. Welch Oct. 5, 1937. R, w c 2,094,862

PRESS FOR PLYWOOD Filed Nov. 26, 1934 3 Sheets-Sheet 2 amen Km Ari/1Wfi. Wick Oct. 5, 1937; A. R. WELCH 2,094,362

PRESS FOR PLYWOOD Filed Nov. 26, 1934 7 v3 Sheets-Sheet 5 Patented Oct.5, 1937 PATENT OFFICE PRESS FOR PLYWOOD Arthur R. Welch, Hoquiam, Wash.,assignor to Harbor Plywood Corporation, Hoquiam, Wash, a corporation ofDelaware Application November 26, 1934, Serial No. 754,826

13 Claims. (Cl. 144-281) My invention relates to presses for such uses.

as the manufacture of plywood. It is particularly designed as a hotplate press for manufacture of plywood wherein the binding or adhesiveagent is a resin which sets by application of heat and pressure. It is,however, adaptable to the manufacture of other products, as for examplecombination or molded panels, wherein boards or panels are formed bysetting a mass of loose material under heat and pressure, or indeed itis useful in the manufacture of plywood according to present practice,with the usual glues.

Very heavy pressure must be employed in presses which employ as a binderfor plywood the resins mentioned. It is not economically possible toprovide a press which will operate upon each individual panel, becauseof the time factor. Such presses, therefore, must receive a considerablenumber of individual panels, all of which are operated upon at oneclosing of the press. Because of the pressure involved and the weightand size of the press plates, which must be of a size to accommodatepanels of maximum area,say 12 x 15 feet, such presses, with the platesresting one upon another, would produce a tremendous pressure upon thelowermost panel. Because of the manner in which plywood is laid uppreparatory to pressing it is not convenient nor economically possibleto dispose the panels on edge, but rather they must be kept flat;therefore the press plates must be superposed horizontally one aboveanother. If too great a pressure is applied to a panel of this sort thewood will be compressed, and it has been found that a pressure of 25,900pounds per square foot will reduce the thickness of the panel by about40%, as a result of which the manufacture in effect loses or wastes 40%of his production, and the product is inferior in quality.

Accordingly it is an object of my invention to provide a press ofsufficient size and weight to apply the pressure to panels up to themaximum sizeand to apply heat to these panels, yet in such a way as toavoid such extremes of pressure as will crush or appreciably reduce thethickness of the panels.

One further disadvantage of applying too.

heavy a weight to the panels is that in addition to the actual shrinkagethe panels will not be of uniform thickness, which is disadvantageous,

and if they are to be brought to uniform thickfore there is in effectthe same wastage from all panels as from that one which has been mostcompressed. Accordingly it is a further object of my invention toprovide such a press which will, within the limits-of permanentdeformation 5 or crushing of the wood, apply a substantially uniformpressure to all panels.

It is a further object to simplify the construction of such presses topermit each plate to be suspended from a plate above it, and by means 0which are simple, inexpensive, and yet thoroughly reliable, so that mostof the plates need no other support than the suspending means connectingthem to a plate above, notwithstanding the cumulative stresses caused bythe weight of 15 all the plates.

Such plates are generally heated by steam; to attain the temperaturesrequired this must be supplied at considerable pressure. It has beenfound extremely troublesome to supply steam to the chambers within suchplates owing to the fact that the press is constantly closing andopening, and it has been considered necessary heretofore to employflexible hose connections, or connections having relatively movableparts, which connections having relatively movable parts were hard tokeep tightly packed. It is therefore another object of my invention toprovide a simple, effective, inexpensive and troubleproof connectionfrom a source of steam supply to each of the several movable pressplates.

Other objects, more especially such as pertain to mechanical details ofmy invention, will be ascertained as this specification progresses.

My invention comprises the novel press, and the novel parts andarrangements thereof, as shown in the accompanying drawings, describedin this specification, and as will be hereinafter pointed out in theclaims. I 40 In the accompanying drawings I have shown my invention in aform now preferred by me, and somewhat diagrammatically.

Figure 1 is an elevation of the press, with parts in open position, andwith parts broken away for better illustration.

Figure 2 is an end elevation of the press in the position of partsillustrated in Figure 1, and Figure 3 is a similar view showing thepress closed.

Figure 4 is a diagrammatic end view, showing the first step in closingthe press, and Figure 5 is a view similar to Figure 4, showing a secondstep in the closing of the press.

Figure 6 is 'a diagrammatic end view of a modi- 55 fled form of thePress, showing the press partially closed.

The press as illustrated is of the type in which a heavy bed .I issupported at a fixed elevation above the floor or the ground, and inwhich a platen 2 is movable upwardly toward the bed I, under theinfluence of press-closing means, illustrated by the cylinders 3 withtheir pistons 30 engaging beneath the platen 2. details of the bed andpress, and of the pistons and cylinders, and the manner of control ofthe latter, are or may be anything which is found suitable or which isconventional, and these details, particularly the controls of thecylinders, have not been illustrated. The bed is shown as formed ofheavy structural members l extending lengthwise of the press andsupported upon columns II, supported from which structural members II]are transverse structural members l2, and finally longitudinalstructural members l3, beneath which is secured the uppermost of thepress plates, which uppermost plate is distinguished by the numeral 4|.The platen 2 is similarly formed, and supports the lowermost of themovable press plates, which is distinguished by the numeral 42. Betweenthese plates 4| and 42 are a number of superposed plates. Normally theseplates are of the intermediate type typified by the plates 43, but thereare preferably provided one or more control plates, of which two areshown in the drawings, designated 44 and 45, which are plates disposedbetween the upper plate and the lower plate and constructed and arrangedto support intermediate plates.

The plates beneath the plates 4|, 44 and 45, respectively, may besuspended from these plates, or in succession from each other within thegroups of intermediate plates, by means such as are illustrated inFigures 2 and 3, wherein it will be seen that links 5, at each end ofthe press, extend from each plate to the plate immediately below it,being received over pins or headed studs 50 and 5| in the respectiveplates. These links 5 may be formed of saw steel, because of its veryconsiderable strength and its flexibility. Each set will support thenext lower plate or a series of plates, yet will tend to contract andbecome round as the press closes, thereby avoiding any danger ofbecoming disengaged from the studs 50 and 5t.

It will now become apparent that the links 5 at the top of the presswould be holding a very great weight if all the plates were suspended insuccession from those above, for each such plate of a size to take apanel 12x 15 feet weighs in the a neighborhood of 10,000 pounds, and thepress is designed to employ about fifteen such plates, and in additionthere would be suspended, to a certain extent at least, the platen 2.Furthermore, if the platen, in moving upward toward the bed, were topick up the several plates in succession, by the time the last oruppermost plate had closed there would be imposed upon the plywood panelbetween the two lowest plates a weight in the vicinity of 150,000pounds, which would be sulficient to materially crush the panels. I havefound it necessary, therefore, to provide means.

to apply a force to the control plates, such as the plates 44 and 45,which force will act in opposition-to the force of the pistons 30tending to close the press, but will eventually be overcome thereby, butwhich in resisting that force will relieve the suspending links 5 of theWeight of allbut a few of the plates, and will relieve the lower pliesThe structural in the press from the great pressure of any considerablenumber of plates above, transmitting the force created by the weight ofthe plate groups directly to the platen 2.

Thus each of the control plates 44 and 45 may be provided with lugs 46and 41, respectively, and there may be supported upon the platen 2cylinders 6 and 1, the pistons 60 and 10, respectively, of which engagethe lugs 46 and 41. A fluid pressure medium-steam or compressed air-issupplied to the cylinders by the respective supply pipes GI and 1|, andthe pressure in such cylinders is maintained constant within certainlimits, at a value to create a force inferior to that exerted by thepistons 30 in closing the press, by suitable means such as the valves 62and 12, and the force developed in these pistons may be so regulated,having proper regard to the pressure of the medium within the cylindersand the area of the pistons, as to produce an upward force on the lugs46 and. sufiicient to support the plates suspended from or supported bythese control plates 44 and 45, respectively.

I have illustrated a press having sixteen plates in all and divided intothree groups. The total number of plates may, of course, be varied, asmay the number within each group, but for clarity of description I shallconfine my discussion of the operation of the press to one havingsixteen plates, divided into three groups, of the type illustrated.

In my sixteen-plate press there are two control plates, numbered 44 and45, supported on the pistons 60 and 10, respectively. In each of thespaces, between the stated control plates, between control plate 44 andthe uppermost plate 4|, and between control plate 45 and the lowermostplate 42, are mounted four intermediate plates 43. As a preliminary stepto the operation of the press the valves 62 and 12 are regulated so thata pressure is maintained within the cylinders 6 and 1 sufficient tocause the pistons 60 and 10 to exert a pressure of approximately 12,500pounds, assuming that the weight of one plate is 10,000 pounds. Thispressure is maintained so that the force exerted by the four pistons 60will aggregate 50,000 pounds, which is the weight of the control plate44 and four intermediate plates. Similarly the combined force exerted bythe pistons 10 should be approximately 50,000 pounds, or the weight ofthe control plate 45 and four intermediate plates. Also the individualvalves 62 and 12 should be regulated so that the pressure in each of thefour cylinders 6 and in each of the four cylinders 1, respectively, isequal, so that the force exerted on the control plates 44 and 45 will bedistributed evenly.

Now in describing a typical closing operation of the press we shallassume that the combined force exerted by the pistons 60 is slightly inexcess of 50,000 pounds, and that exerted by the pistons 10 is likewiseslightly in excess of 50,000 pounds. With the press in the openposition, therefore, the upper set of four intermediate plates 43,between plates 4| and 44, will be suspended one from the other, and theuppermost plate 43 will be suspended from the plate 4|. The uppermostlinks 5 will therefore support a weight of 40,000 pounds, the next lowerset of links will support a weight of 30,000 pounds, the next lower set20,000 pounds, the next lower set of 10,000 pounds, and the next lowerset, interconnecting the plate 44 and the plate 43 immediately above it,will be substantially untensioned. The reason that this last mentionedset of links will be substantially untensioned is that the plate 44 andthe tour plates 43 therebeneath are supported by the pistons 60.Therefore the links interconnecting the plate 44 with the plate 43immediately therebeneath will supporta weight of 40,000 pounds, the nextlower set of links 30,000 pounds, the next lower set 20,000 pounds, thenext lower set 10,000 pounds, and again the set of links interconnectingthe plate with intermediate plate 43 next thereabove will besubstantially untensioned. Again the reason for the lack of tension inthe last mentioned set of links is that the pistons I0 support the plate45 and the four intermediate plates suspended therefrom by reason of theforce of 50,000 pounds exerted on the members 41 by these pistons. Againthe weight supported by the links below plate 45 will decreasesuccessively as in the sets of plates thereabove, until the linksinterconnecting plate 42 and the plate immediately thereabove will besubstantially untensioned, since "plate 42 is supported directly fromtheplaten 2.

The closing action is accomplished entirely by pressure being exerted onthe pistons 30 within the cylinders 3, the pressure in the cylinders 6and 1 remaining constant throughout the closing and opening operations.Since in open position,

' however, the upper set of four intermediate plates 43 is supportedfrom the plate 45 the pressure exerted by thepistons 30 will be 110,000pounds, made up of (1) the pressure exerted by the cylinders 6 equal tothe weight of the plate 44 and the four plates 43 suspended therefromand transmitted through pistons 60; (2) the pressure of the cylinders 1which-is equivalent to the weight of the plate 45 and the four plates 43suspended therefrom, transmitted through the pistons 10, and (3) theweight of the plate 42 plus, in addition to this 110,000 pounds, theweight of the cylinders 3 and I and the pistons 60 and m and the platen2. When the press is closed the only additional weight borne by thepistons 30 is that of the upper set of four intermediate plates, whichis 40,000 pounds plus the pressure exerted on the least pressed panel.

When the press is to be closed the pressure in the cylinders 3 isincreased, and the platen 2 starts to rise. The plate 44 and the plates43 suspended therefrom, supported as they are directly from the platen 2through the pistons 40 and cylinders 6, will be carried bodily upward.Likewise the plate 45 and the plates 43 suspended therefrom, supporteddirectly from the platen '2. through the pistons l4 and cylinders i,will be carried bodily upward, as will the plate 42, which is mounteddirectly on the platen 2. The upper set of plates 43, it will beremembered, is suspended when the press is open from the plate 44, andhence the position of these plates will be unaffected by upward movementof the pistons 34. As a result the first space to close is that betweenthe plate 44 and the plate 43 next thereabove. Now as the upwardmovement of the platen continues, the plate 44 will begin to assume theweight of the plate 43 next thereabove through the medium of theinterposed panel. If the plate 44 were to take the whole weight of thisnext above plate 43, the total force on the plate 44 including the fourplates 43 suspended therefrom would be 60,000 pounds, but the forceexerted by the pistons 60 is only slightly in exces of 50,000 pounds.Hence although the space above the plate 44 is now closed, before theweight of the plate 43 next thereabove would be assumed, the resistanceof the pistons60 would be overcome, and they would remain stationary foran interval while the platen raised the cylinders 6 with respectthereto.

Since the pistons 60, the plate 44, and the plates 43 suspendedtherefrom are all now stationary, although the platen continues to moveupward, the pistons 10, which still remain in their fully extendedposition, will raise the plate 45 to close the space between it and themomentarily stationary plate 43 next thereabove. When this gap is closedthe plate 45 would tend to assume the weight of this plate 43, but ifthis were accomplished the total force on the'plate 45, including theweight of the four plates 43 suspended therefrom, would be 60,000pounds, which would exceed the critical force of 50,000 pounds, orslightly more, for which the set of pistons 10 is set. Hence uponcontinued upward movement of the platen pistons I0 would remainstationary v and cylinders 1 would move upward relatively thereto, whilecylinders 6 would continue to move upwardly relatively to pistons 60.

At this stage all of the plates 4|, 44 and 45 and the plates 43suspended therefrom are stationary, but the plate 42 mounted directly onthe platen 2 is still moving upward, so that the space between it andthe plate 43 next thereabove will be closed, and this plate will assumethe weight of the lowest plate 43.

With the weight of the lowest plate 43 removed from suspension by theplate 45, the latter plate will assume the weight of the plate 43 nextthereabove, in turn relieving the plate 44 from the suspended weight ofthis plate 43. Likewise, when thus relieved the plate 44 will assume theweight of. the plate 43 next thereabove. Now two plates will besupported directly upon the platen 2, and only three plates 43 will besuspended from l3. Upon further upward movement of the platen the spacesecond above plate 44 will now be closed, and. in turn the space secondabove plate 45 and second above plate 42 will in turn be closed. Theclosing process then continues in this fashion until all the plates-aremoved into the position shown in Figure 3. In this position the plate 44will no longer support any plate 43 therebelow, but will support theplate 43 there above. Similarly the plate 45 will no longer sup port anyplate 43 therebelow, but will support the plates 43 between the plate 44and plate 45. The intermediate plates 43'below plate 45 will besupported directly by the platen 2, While no plate will be suspendedfrom plate M.

It the pressure in the cylinders i and l is set at a value so that thepistons will support a curs. The spaces above plates 44 and 45 willremain closed as long as no weight is added to these plates. Thereforethe first space to open will be that immediately below plate 45. Withthe added weight of the plate immediately below plate 43 the spaceimmediately below plate 44 will start to open, and when the weight ofthis plate begins to be suspended from 44 the space immediately belowplate 41 will begin to open, and the spaces will continue to open insuccession until the press has reached the full open posi-, tion shownin Figure 2. Of course, if the cylinder pressures are such that theforces supplied by the two sets of pistons are slightly under 50,- 000pounds, then the first space to open will be that immediately belowplate 4!, then that immediately below plate 44, then that immediatelybelow plate 45, and so on. Thus opening and closing of the press isaccomplished in a short time with a minimum of shock and with onlysufficient pressure to produce the setting of the binder, butinsufiicient to affect the wood of the plies. The minimum pressure, ofcourse, is applied to the panel in the space last to close, and themaximum pressure will be on the panels resting on the plates 42, and 44,which will be approximately 40,000 pounds in excess of the minimumpressure, which is the weight of the press plates supported by thesepanels above the control plate.

In order to supply steam to the interior chambers of these plates Iprovide each of them with an inlet connection as illustrated at 8 by wayof example. The steam supply may come from a source such as the header80, and between the header and the several inlets 8 are connectionsformed of pipes, including particularly the length 8! which may in turnbe connected to the inlet 8 by a riser 82, the length 8!, which isconnected rigidly to the header, being of such length with respect tothe required movement of its connected inlet 8 and the limit ofelasticity of the pipe itself, of which it is formed, that in flexingits end through this amount of movement the limit of elasticity will notbe reached. In consequence the pipe, though rigidly connectedthroughout, will flex without being damaged; there is no packing jointrequired, and the difiiculties of a flexible steam hose are eliminated.

Whereas in the form shown in Figures 4 and 5 the two cylinders 6 and 'lare both shown supported from the platen 2, in Figure 6 the same resultsare achieved by a modification of that arrangement, in which the shortercylinder, 7', which supports the plate 45, in turn supports the cylinder66, the piston 6'! of which supports in turn the plate 44. In this form,of course, the force exerted by the piston l0 will be approximatelytwice as great as the force exerted by the piston 6 since the lowerpiston must support not only the lower set of plates supported by orfrom plate 45, but through the piston 61, must support also the set ofplates supported by or from plate 44. The same results are achieved, thepiston 67 first yielding, and then the piston 10 yielding, thetwothereafter yielding alternately until the last space, that immediatelybelow plate 45, is closed.

What I claim as my invention is:

l. A press for the purposes described comprising a bed, a platen, and aplurality of independently movable superposed plates therebetween, meansto move the platen towards the bed, to contract the several plates forpressing the work therebetween, and means movable with the platen andsupporting an intermediate plate therefrom, and operable to transmit acontracting force to plates between such intermediate plate and the bed,and said means being contractable simultaneously with contraction ofplates between such intermediate plate and the platen.

2. A press for the purposes described comprising a bed, a platen, aplurality of superposed plates therebetween, means to move the platentowards the bed, to contract the several plates for pressingthe worktherebetween, means movable with the platen and supporting a plateintermediate the bed and platen, and operable to transmit a contractingforce to plates between such intermediate plate and the bed, and saidmeans being contractable under the force of the platen-moving means incontracting the plates between such intermediate plate and the platen, asecond like means movable with the platen and similarly supporting adifierent plate intermediate the first intermediate plate and the bed,and similarly contractable.

3. A press for the purposes described comprising an upper and a lowerpressure member, a plurality of superposed plates therebetween, means tomove the lower member towards the upper member, to contract the severalplates for pressing the work therebetween, a cylinder and piston movabletherein independent of said moving means, both supported upon and formovement with the lower member, and supporting a plate intermediate theupper and lower members, and means to control the pressure of a fluidmedium within the cylinder supported upon the lower member, to transmita contracting force to plates above said intermediate plate, but tomaintain the pressure of the fluid medium in said cylinder inferior tothat of the moving means, whereby the cylinder and piston will yieldduring contraction of plates below such intermediate plate.

4. A press for the purpose described comprising an upper and a lowerpressure member, a plurality of superposed press plates therebetween,moving means to effect approach of the two pressure members to contractthe several plates for pressing the work therebetween, and means to,apply a force in one direction to an intermediate plate, the reactionthereof acting in opposition to but being inferiorto the force of themoving means, to partially support the weight of said intermediate plateand plates thereabove during contraction of the press plates.

5. A press for the purpose described comprising an upper bed and a lowerplaten, a plurality of superposed plates therebetween, means to suspendeach plate in succession from a plate thereabove, means to effectapproach of the platen towards the bed to contract the several platesfor pressing the work therebetween, and means reacting from the platento apply a yieldable force to an intermediate plate sufficient tosupport the weight of such intermediate plate and plates suspendedtherefrom.

6. A press for the purpose described comprising an upper bed and a lowerplaten, a plurality of superposed plates therebetween, links suspendingeach plate in succession from the plate above, means to move the platenupward towards the bed to contract the several plates for pressing thework therebetween, and means movable with the platen to support anintermediate plate and plates suspended therefrom, and yieldable withrespect to the platen, for contraction of the plates below suchintermediate plate.

7. The combination of claim 6, wherein the links comprise closed loopsof saw steel or the like.

8. A press for the purpose described, comprising a bed, a platen, aplurality of independently movable superposed press plates therebetween,means operable to draw all said plates together, to close the press, andmeans engaging an intermediate plate in closed position of the press tosupport its weight independently or the other press plates.

9. A press for the purpose described comprising an upper and a lowerpressure member, su- 5 perposed plates therebetween including a controlplate, a plurality of plates thereabove adapted to be supported by saidcontrol plate when the press is in closed position, an equal number ofplates below said control plate and suspended therefrom when the pressis in open position, means to eifect approach of thetwo pressure membersto contract the several plates for pressing the work therebetween, andmeans engaging said control plate to exert a supporting force thereonsubstantially equal to the combined weight of said control plate and thesaid plurality of plates thereabove.

10. A press for the purpose described comprising a fixed upper pressuremember and a movable lower pressure member, superposed platestherebetween including a control plate, a plurality of plates thereaboveadapted to be supported by said control plate when the press is inclosed position, an equal number of plates below said control plate andsuspended therefrom when the press is in open position, means to raisesaid lower pressure member to contract the several plates for press-'ing the work therebetween, cylinders and pistons therein supported fromsaid lower pressure member and engaged between such member and saidcontrol plate, to exert a supporting force directly on said controlplate of a value substantially equal to the combined weight of saidcontrol plate and the said plurality of plates thereabove.

11. A press for the purpose described comprising an upper and a lowerpressure member, superposed plates therebetween including a controlplate, a plurality of plates thereabove adapted to be supported by saidcontrol plate, and a plurality of plates below said control plateadapted to be suspended therefrom, moving means to effect approach ofthe two pressure members to contract the several plates for pressing thework therebetween, means engaging said control plate to exert a constantforce thereon equal to the weight or the control plate plus the weightof a predetermined number of additional plates, and

'means operable to assume, successively, the

weight of plates suspended from said control plate, thereby enablingsaid control plate to support, successively, the weight of platesthereabove, as said moving means is operated to close 5 the press.

12. A press for the purpose described comprising an upper and a lowerpressure member, superposed plates therebetween, including a controlplate, one or more upper intermediate plates 10 betweensaid controlplate and said upper pressure member, and one or more lower intermediateplates between said control plate and said lower pressure member, saidlower intermediate plates being of an aggregate weight equal to theaggre- 15 gate weight of said upper intermediate plates, means tosuspend said lower intermediate plates from said control plate, movingmeans to effect approach of the two pressure members to contract theseveral plates for pressing the work 20 therebetween, and means engagingsaid control plate to exert a supporting force thereon substantiallysufiicient to support from said control plate a weight equal to theaggregate weight of the upper intermediate plates, but insufficient to25 support a weight appreciably in excess of such an aggregate weight.

13. A press for the purpose described comprising an upper and a lowerpressure member, superposed plates therebetween, including a con- 30trol plate, one or more upper intermediate plates between said controlplate and said upper pressure member, and one or more lower intermediateplates between said control plate and said lower pressure member equalin number to the num- 35 ber of said upper intermediate plates, means tosuspend said lower intermediate plates from said control plate, movingmeans to eiiect approach of the two pressure members to contract theseveral plates for pressing the work therebetween, 40

